Disclosed embodiments relate generally to aviation electronics (avionics). More particularly, disclosed embodiments relate to terrain awareness systems and methods.
Preventing an aircraft from operating in an unsafe region is important in the aviation industry. It is also important to prevent aircraft from operating in unapproved regions. Several types of terrain awareness systems have been employed to help achieve this goal. Two primary examples of these types of systems include a ground proximity warning system (GPWS) and an enhanced ground proximity warning system (EGPWS). An EGPWS is sometimes also referred to as a terrain awareness warning system (TAWS).
One type of GPWS is frequently used in regions of operation which are near airports. This type of GPWS utilizes on-board sensing of where the aircraft is relative to airport landing sensors. Generally, this type of GPWS does best when the terrain near an airport is relatively flat. EGPWS or TAWS use terrain data bases and aircraft state information to alert the flight crew when an unsafe situation, with respect to terrain and obstacles, is detected. These systems may also provide terrain situation awareness when no unsafe terrain or obstacle situation exists.
These conventional systems do an admirable job of avoiding controlled flight into terrain (CFIT) situations, providing the flight crew with audible and/or visible warnings when such a dangerous situation occurs or is imminent. However, there are several limitations to these types of systems. For example, these systems are dependent upon the availability and validity of the terrain and obstacle database. With the possibility of large buildings being constructed but not updated in terrain map databases, as well as the possibility of other unmapped or mis-mapped terrain or obstacles, the validity of such terrain map databases can be less than completely certain. Also, once obtained, convincing regulatory authorities of their trustworthiness presents additional challenges. Further, as the terrain map databases contain more and more information, the memory requirements for storing and processing the databases have increased significantly. Increases in memory requirements can be costly in avionics applications.
Another limitation of existing terrain awareness systems is the limited amount of time which they allow for a flight crew to react to a detected threat. Frequently, such systems provide the flight crew with a warning approximately one minute or less prior to impact of the aircraft with the terrain or obstacle, though in some situations the warning may be more than a minute in advance. While this may be sufficient time to avoid the CFIT situation, it is not in all cases. Further, the maneuvers required to avoid the terrain or obstacle, given such a limited amount of time to react, may not be ideal for certain flight situations, such as commercial airline flights with passengers.